1. Field of the Invention
The present invention generally relates to an optical pickup device. There is 90 degree phase shift between linear polarization light from an laser diode reflected by an optical disk, which feedback to the original laser diode and linear polarization light from the original laser diode.
2. Background Description
FIG. 1 shows all components in an ordinary optical disk system. At first, laser diode 11 emits a p-type linear polarized light to polarized beam splitter 12. Through polarized beam splitter 12 and quarter wave plate 13, the light becomes circular polarized light to optical disk 16. Corrected by collimator lens 14 and objective lens 15, the light reflected by optical disk 16 comes back with original optical path. That is to say, through objective lens 15 and collimator lens 14, the reflected light with left-hand circular polarization enters into quarter wave plate 13 and polarized beam splitter 12. Finally, the light with s-type linear polarization enters to photodetector 17.
In this optical path with disk signal from optical disk, there are few signals which feedback to laser diode 11 by the property of polarized beam splitter 12. The partial signa with p-type linear polarization through polarized beam splitter 12 enters the laser diode 11. It makes intensity noise and influences the original p-type polarized light from laser diode 11. In FIG. 2, the photodetector 17 detects the related intensity noise which makes the bad influences of precision of detecting signals.
According to the defect of used optical pickup system, this invention has been implemented an optical pickup system and its optical path by the optical property to reduce the signal intensity noise and increase the precision of detecting signal, which can improve the defect of used optical pickup system.